fact.hpp

// algocpp/math/fact.hpp
//
// This file is part of algocpp and is copyrighted by algocpp.
// If used, it must comply with the MIT License.

#ifndef ALGOCPP_MATH_FACT
#define ALGOCPP_MATH_FACT

#include <stdexcept>

#if !defined(ALGOCPP_DONT_LIB) && __has_include(<boost/multiprecision/cpp_int.hpp>)
#include <boost/multiprecision/cpp_int.hpp>
#endif

namespace algocpp
{
	namespace math
	{

		inline unsigned long long fact(long long x)
		{
			if (x < 0)
			{
				throw std::invalid_argument("The factorial of negative numbers is undefined.");
			}

			unsigned long long result = 1;
			for (long long i = 1; i <= x; ++i)
			{
				result *= i;
			}
			return result;
		}

#ifdef BOOST_MP_CPP_INT_HPP
		inline boost::multiprecision::cpp_int fact(boost::multiprecision::cpp_int x)
		{
			if (x < 0)
			{
				throw std::invalid_argument("The factorial of negative numbers is undefined.");
			}

			boost::multiprecision::cpp_int result = 1;
			for (boost::multiprecision::cpp_int i = 1; i <= x; ++i)
			{
				result *= i;
			}
			return result;
		}

		inline boost::multiprecision::int1024_t fact(boost::multiprecision::int1024_t x)
		{
			if (x < 0)
			{
				throw std::invalid_argument("The factorial of negative numbers is undefined.");
			}

			boost::multiprecision::int1024_t result = 1;
			for (boost::multiprecision::int1024_t i = 1; i <= x; i++)
			{
				result *= i;
			}
			return result;
		}
#endif

	}
}

#endif // ALGOCPP_MATH_FACT